 209 Training Depot.Throughout the early 1920s pilots and observers of seaplanes were trained at Lee-on-Solent under a variety of names; from 1921 the base was renamed the RAF Seaplane Training School, and from 1923, the RAF School of Naval Co-operation.Although the school now concentrated on observer training, from 1925 all naval aircrew were provided by the RAF, and training of naval officers as observers ceased.